Needle unit

ABSTRACT

A syringe comprising a barrel ( 10 ), a plunger ( 11 ) and a needle unit ( 12 ). The needle unit ( 12 ) has a needle ( 30 ) which is biased inwardly of the barrel ( 10 ) but whose inward movement is blocked by a stop element ( 34 ). The needle ( 30 ) is released from the stop element ( 34 ) in response to the plunger ( 11 ) reaching the final part of, or the conclusion of, its delivery stroke to allow retraction of the needle ( 30 ). The barrel ( 10 ) of the syringe is provided with a seal ( 38 ) which contacts an outer peripheral surface of the stop element ( 34 ).

This invention relates to fluid-handling devices, in particular,hypodermic syringes, and is particularly concerned with needle unitsadapted to be coupled to syringe barrels from which fluid is to bedispensed via the needle.

In our prior International Patent Application No. PCT/GBO2/01865(WO-A-02/087669), there is disclosed a syringe comprising a barrel and aneedle unit comprising a housing connected or connectable at one end toa barrel , a needle-mounting hub, a biasing element arranged to urge thehub inwardly of the barrel, and a stop element blocking inward movementof the hub into the barrel until the hub is released from the stopelement in response to a plunger associated with the barrel reaching thefinal part of, or the conclusion of, its delivery stroke to allowretraction of the needle-mounting hub into the hollow plunger. Such aneedle unit is referred to herein as a “needle unit as defined”.

In the needle unit of International Patent Application No.PCT/GB02/01865 (WO-A-02/087669), the stop element includes an integralseal, in particular a lip seal, to ensure that the liquid delivered fromthe barrel passes through the needle.

One problem with a needle unit as defined is that the needle retractionmechanism may inadvertently be activated prematurely. For example,during transport of a syringe comprising the needle unit, the plungermay be depressed with sufficient force to activate the retractionmechanism. Alternatively, if the needle unit is stored separately fromthe barrel of the syringe, then the stop element may be accidentallyknocked, releasing the hub and retracting the needle. Once the needlehas been retracted, the needle unit cannot be used and is wasted.

The present invention seeks to provide improvements in needle units asdefined and syringes comprising such needle units. However, it is to beappreciated that the provision of a hollow plunger is not an essentialfeature of the invention since, for example, the plunger may comprise apiston mender and a separate rod in which case the needle-mounting hubis retracted into the barrel adjacent to the rod rather than within theplunger as such.

According to one aspect of the present invention there is provided asyringe having a needle unit as defined and in which the barrel or apart for connecting the needle housing to the barrel is provided with aseal which contacts an outer peripheral surface of the stop element.

The seal may be a lip seal which tends to deflect radially inwardly whenthe fluid is pressurised during the delivery stroke of the plunger.

The seal may be integral with the barrel or said connecting part.

The housing or the connecting part may be readily connectable to thebarrel but once connected the arrangement may be such that it cannot befreed from the barrel, at least not without the application of forcessubstantially in excess of the force required to effect the connectionto the barrel.

The housing or the connecting part may be designed to snap engage withthe barrel.

According to a second aspect of the present invention there is provideda needle unit in which the stop element is arranged to snap engagewithin the housing to couple the needle hub to the housing and retainthe biasing element in a stored energy condition.

The biasing element is typically a coiled compression spring which isarranged in encircling relation with the needle.

According to a further aspect of the present invention there is provideda needle unit as defined and a sheath for enclosing the needle, thehousing including one or more openings through which the sheath and stopelement can make contact. The sheath and stop element may make contactso that the sheath can be used to apply axial force to the stop elementwithout significantly stressing the coupling between the stop elementand the hub.

This aspect of the invention is particularly advantageous where asliding type sealing action is provided between the outer periphery ofthe stop element and an adjacent component. The sliding type sealingaction may for example be provided by means of a lip seal on the barrelor an intermediate part for connecting the housing to the barrel.

Alternatively, or in addition, the sheath and stop element may makecontact so that the sheath restricts movement. of the stop element, toprevent release of the needle mounting hub from the stop element. Thusretraction of the needle is prevented until the sheath is removed.

In one embodiment, the housing is provided with one or more openingswith which a projection or projections on the stop element snap engageand the openings are so arranged that a portion or portions of thesheath can be brought into abutment with said projection(s). In anotherembodiment, the projection or projections on the stop element engagewith an inwardly directed rib or the like on the housing. The projectionor projections may have an inclined outer face such that they may rideover the inner surface of the housing before they snap engage with theopenings in the housing. It will be appreciated that the engagementbetween the stop element and the housing may be effected in other ways;for example, projections on the housing may snap engage with appropriateformations o n the stop element.

The hub and the stop element may be formed as plastics mouldings in sucha way that the stop element is axially captive with the hub, the stopelement and the hub being disengaged from each other during said finalpart of, or at the conclusion of, the delivery stroke of the plunger toallow the biasing element to drive the needle into the hollow plunger.

The manner in which the stop element and the hub interact with eachother, the design features and production materials for these componentsand the biasing element may be as disclosed in International PatentApplication No. PCT/GB02/01865 (WO-A-02/087669). Also the manner inwhich the plunger interacts with the stop element and the hub may be asdisclosed in International Patent Application No. PCT/GB02/01865(WO-A-02/087669). In particular, the plunger is, in some embodiments,associated, at its forward end, with a portion which is severable inresponse to movement of the plunger over the final part of, or at theconclusion of, its delivery stroke to allow retraction of the needlemounting hub into the hollow plunger.

The plunger may comprise a piston member and separate hollow rodarrangement as disclosed in our PCT Patent Application entitled“Prefilled Fluid Handling Device” having the same priority date, theentire disclosure of which is incorporated herein by this reference.

The stop element may be of generally cylindrical configuration andcomprise a forward portion within the housing and a rearward portion oftapering configuration.

The invention will now be described by way of example only withreference to the accompanying drawings, in which:

FIG. 1 is a schematic longitudinal sectional view of one form of needleunit and part of the barrel of a hypodermic syringe in accordance withthe present invention;

FIG. 2 is a perspective cut away view of another form of needle unitshown in conjunction with the barrel of a prefilled syringe.

The various aspects of the present invention may be implemented in afluid handling device comprising a barrel for containing fluid to bedelivered through a needle, a needle-mounting hub at one end of thebarrel, a biasing element arranged to urge the hub inwardly of thebarrel, a stop element blocking inward movement of the hub into thebarrel, a hollow plunger which is movable within the barrel to deliverfluid from the barrel via the needle and is associated at its forwardend with a portion which is severable in response to movement of theplunger over the final part of, or at the conclusion of, its deliverystroke to allow retraction of the needle-mounting hub into the hollowplunger, the hub and the stop element being formed as plastics mouldingsin such a way that the stop element is axially captive with the hub, thehub and stop element being disengaged during said final part of, or atthe conclusion of, the delivery stroke of the plunger to allow thebiasing element to drive the needle into the hollow plunger.

Referring firstly to FIG. 1, a disposable medical syringe comprises ahollow barrel 10 which accommodates a plunger 11 generally of the formdisclosed in International Patent Application No. PCT/GB02/01865(WO-A-02/087669) or PCT/GB00/04573 (WP-A-0142104), the plungercomprising a rim portion 13A and a blocking portion 13B. The barrel 10is provided at its forward end with a needle unit 12 comprising ahousing 14 which is coupled to the barrel 10 by any suitable means 15such as snap engaging formations or a screwthreaded connection whichmay, in each case, be irreversible so that the needle unit ispermanently connected to the barrel.

A needle-mounting hub 22 is accommodated within the housing 14 and isencircled by a coiled compression spring 24 which engages at its forwardend with a flange 28 of a conical section 20 of the housing and at itsrear end with a radial shoulder 26 on the hub 22. The spring 24 servesto bias the hub 22 and needle 30 inwardly relative to the barrel 12 (andoutwardly relative to the needle unit housing).

The hub 22 is of generally cylindrical configuration and has an axialbore for reception of the needle 30. The bore may be a throughbore andmay be of tapering configuration to allow the needle to be fitted to thehub as a press-fit or by spin-welding.

Rearward movement of the hub and needle assembly (to the right as viewedin FIG. 1) is prevented by a stop element in the form of a crown 34which is carried by hub 22. The crown 34 is of generally cylindricalconfiguration and comprises a forward portion 36 within the housing 14and a rearward portion 40 of tapering, e.g. generally conical,configuration. The rearward portion 40 enters the forward end of thebarrel 10 and co-operates with a lip seal 38 which flares radiallyinwardly and is resiliently flexible so that, on insertion of the crownportion 40, it is deflected radially outwardly so that it then bearsresiliently against, and makes effective sealing engagement with, theouter peripheral surface of the crown portion 40. The lip seal 38 may beintegral with the barrel which itself may be a plastics moulding.

The hub and crown are produced as plastics mouldings by two-shotmoulding which serves to integrate the two components and render themcaptive with each other so that they effectively constitute a one-piececomponent designed to separate from each other at the interface betweenthe hub and the crown when subjected to a predetermined forwardlydirected axial force. At the interface 45 between the hub and crown, thecomponents may have interfitting formations, e.g. mating frusto-conicalsurfaces, which may determine at least in part the force needed toseparate the two components. Separation of the hub from the crown may beeffected in the manner described in detail in International PatentApplication No. PCT/GB02/101865.

The crown 34 is engaged with the housing 14 by snap engagement oflaterally directed projections or latches 50 with openings 52 in thewall of the housing 14. The outer faces 54 of the projections 50 areinclined so that as the crown is inserted Into the housing, theprojections may ride over the inner surface of the housing and thespring outwardly to effect snap engagement. This allows the crown, huband spring to be assembled to the housing in a simple and effectivemanner by pushing the assembly of crown, hub and spring (against thebiasing action of the spring) into the housing until the latches 50spring into the openings 52 and prevent return movement of the assembly.

Once the crown, hub and spring assembly has been fitted to the housing,the needle unit is fitted to the barrel. This involves pushing the crowninto the barrel against the resistance created by the lip seal 38. Toavoid stressing the connection between the hub and the crown at thisstage with the consequent risk of prematurely freeing the hub from thecrown, the force needed to properly engage the crown with the lip sealis applied along a pathway which by-passes the hub/crown connection 45.More specifically, the force is applied directly to the crown (seearrows X) through the openings 52 by way of a sheath (not shown, but seeFIG. 2 which illustrates the form that the sheath may take). The sheathserves to shield the needle and includes ribs arranged to contact thelatches 50 via the openings 52.

After the needle unit has been assembled to the barrel and the syringeis about to be used to administer an injection, the sheath is removed.

Referring now to FIG. 2, the syringe shown is suitable for prefilledapplications as disclosed in our PCT Patent Application entitled“Prefilled Fluid Handling Device” and having the same priority date, theentire disclosure of which is incorporated herein by this reference. Thesyringe includes a barrel 110, a piston unit 114 and a hollow rod 122for displacing the piston member 114 towards the dispensing outlet 112of the barrel so as to discharge a prefilled amount of drug or othercomponent from the barrel and through the needle 120 of the needle unit118. In FIG. 2, the needle unit is shown enclosed in a sheath 160 but,in practice, the sheath is removed before the contents of the barrel aredischarged through the needle.

Features relating to the piston member 114, the barrel 110 and the rod122 are described in said PCT Patent Application and reference should bemade thereto for specific details. Briefly, the piston member comprisesa central glass blocking portion 136 received in but severable ordislodgeable from a plastics rim portion 130 provided with a siliconerubber seal 138 having an integral extension 144 which overlies theforward face of the piston member to eliminate any risk of constituentsof the plastics moulding contaminating the contents of the chamber 116.

The needle unit in FIG. 2 comprises a housing 162 having a relativelynarrow forwardly extending section 164 and an enlarged trailing section166, there being openings 163 in the housing 162 at the junction betweenthe sections 164 and 166. As In the embodiment of FIG. 1, the housing162 accommodates an assembly comprising a hub 169, a crown 170 and acoiled compression spring 172 which is trapped in a compressed, energystoring state between the forward end of the section 164 and a shoulder174 on the hub 169. This assembly can be fitted to the housing in thesame manner as described in connection with FIG. 1, i.e. by insertingthe assembly until the latches snap enagage in the region of theopenings 168. In this case, the snap engagement is between the latches176 and an inwardly directed rib 178. The hub and crown are coupledtogether at the interface 180 in the manner previously described so thatthe hub can be released from the crown to allow needle retraction duringthe final part of or on completion of the forward stroke of the pistonmember 114.

In this embodiment, instead of providing the lip seal on the barrel (inthis case, a glass barrel), the lip seal 179 (see the detail view, FIG.2A) is provided on an intermediate plastics component 182 which couplesthe housing 162 of the needle unit to the dispensing outlet 112. Theintermediate component 182 may engage with the outlet 112 in anysuitable manner, e.g snap engagement or screwthreaded connection(irreversible or otherwise). The component 182 may be fitted to thebarrel outlet 112 before it is engaged with the housing 162 or it may beinitially fitted to the housing 162 and then coupled to the barreloutlet 112. To ensure that the interface 180 is not stressed whileeffecting sliding engagement with the lip seal 179, the sheath 160 canbe used to apply the necessary force directly to the crown 170 via theopenings 168. To this end, the sheath is provided with Internal ribs 184which, when the sheath is fitted over the housing 162, contact thecrown, e.g. the forward ends of the latches 176 at locations 186.

When the sheath 160 is in place enclosing the needle unit, the frictionbetween the sheath 160 and the housing 162 holds the sheath 160 inposition relative to the needle unit. Any forward force on the crown 170is transmitted via the latches 176 to the internal ribs 184 of thesheath 160. Thus, provided that the frictional force between the sheath160 and the housing 162 is not exceeded, the sheath 160 presents theforward movement of the crown 170 and any stress on the interfacebetween the hub 169 and the crown 170. Accordingly, while the sheath 160remains in place the possibility of the crown being inadvertently movedforward, separating from the hub 169 and causing premature retraction ofthe hub 169 and the needle 120 is reduced. This minimizes thepossibility of the needle being inadvertently retracted, for example bythe crown 170 being knocked as the needle unit is fitted to the barrel110.

In practice, the prefilled syringe barrel will initially have a bung inits outlet 188 to retain the drug or other component within the chamberdefined in the forward end of the barrel by the piston member 114. Whenthe syringe is to be used to inject a patient, the bung is removed andthe needle unit is fitted to the outlet 188 using the sheath to ensurethat the interface between the hub and crown is not stressed during thefitting operation.

Whilst endeavouring in the foregoing specification to draw attention tothose features of the invention believed to be of particular importance,it should be understood that the Applicant claims protection in respectof any patentable feature or combination of features disclosed hereinand/or shown in the drawings whether or not particular emphasis has beenplaced on such feature or features.

1-18. (canceled)
 19. A syringe comprising a barrel, an associatedplunger and a needle unit, said needle unit comprising a housingconnected to one end of the barrel, a needle-mounting hub, a biasingelement arranged to urge the hub inwardly of the barrel, and a stopelement blocking inward movement of the hub into the barrel until thehub is released from the stop element in response to the plungerreaching the final part of, or the conclusion of, its delivery stroke toallow retraction of the needle-mounting hub, characterized in that thebarrel, or a part for connecting the needle housing to the barrel, isprovided with a lip seal which contacts an outer peripheral surface ofthe stop element and which tends to deflect radially inwardly when afluid within the barrel is pressurized during the delivery stroke of theplunger.
 20. The syringe according to claim 1 wherein the lip seal isintegral with the barrel or said connecting part.
 21. The syringeaccording to claim 1 wherein the stop element is arranged to snap engagewith the housing to couple the hub to the housing and to retain thebiasing element in a stored energy condition.
 22. The syringe accordingto claim 1 including a sheath for enclosing the needle of the needleunit, the housing including one or more openings through which thesheath and stop element can make contact.
 23. The syringe according toclaim 22 wherein the stop element is coupled to the needle mounting huband the sheath and the stop element can make contact so that the sheathcan be used to apply axial force to the stop element withoutsignificantly stressing the coupling between the stop element and thehub.
 24. The syringe according to claim 22 wherein the sheath and thestop element can make contact such that the sheath restricts movement ofthe stop element, to prevent release of the needle mounting hub from thestop element.
 25. The syringe according to claim 22 wherein one or moreprojections on the stop element engage wit the openings of the housing,the openings being arranged so that one or more portions of the sheathcan abut with one or more projections.
 26. The syringe according toclaim 25 wherein the or each of the projections on the stop elementengage with an inwardly directed rib or the like on the housing.
 27. Thesyringe according to claim 25 wherein the or each of the projections onthe stop element has an inclined outer face such that it may ride overthe inner surface of the housing before snap engagement with theopenings.
 28. The syringe according to claim 1 wherein the plunger ishollow and retraction of the needle-mounting hub is into the hollowplunger.
 29. The syringe according to claim 1 wherein once the housingor the connecting part is connected to the barrel, the force required tofree the housing or the connecting part from the barrel is substantiallyin excess of the force required to effect the connection to the barrel.30. The syringe according to claim 1 wherein the housing or theconnecting part is engageable with the barrel with a snap fit.
 31. Thesyringe according to claim 1 wherein the biasing element is a coiledcompression spring, arranged in encircling relation with the needle. 32.The syringe according to claim 1 wherein the needle mounting hub and thestop element are formed as plastics molding such that the stop elementis axially captive with the hub, the stop element and the hub beingdisengageable from each other during said final part of, at theconclusion of, the delivery stroke of the plunger to allow retraction ofthe needle-mounting hub.
 33. The syringe according to claim 1, whereinthe plunger comprises a piston member and a separate hollow rod.
 34. Thesyringe according to claim 28 wherein the plunger is associated, at itsforward end, with a portion which. is severable in response to movementof the plunger over the final part of, or at the conclusion of itsdelivery stroke, to allow retraction of the needle mounting hub into thehollow plunger.
 35. The syringe according to claim 1 wherein the stopelement is of generally cylindrical configuration and comprises aforward portion within the housing and a rearward portion of taperingconfiguration.